tcg/wasm: Add tcg_target_init function

This commit adds tcg_target_init, aligning it with the Wasm backend's
register and stack usage.

Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>

Author: ktock

tcg/wasm/tcg-target.c.inc

@@ -2812,3 +2812,32 @@ static int tcg_out_tb_end(TCGContext *s)
 
     return 0;
 }
+
+static void tcg_target_init(TCGContext *s)
+{
+    /* The current code uses uint8_t for tcg operations. */
+    tcg_debug_assert(tcg_op_defs_max <= UINT8_MAX);
+
+    /* Registers available for 32 bit operations. */
+    tcg_target_available_regs[TCG_TYPE_I32] = BIT(TCG_TARGET_NB_REGS) - 1;
+    /* Registers available for 64 bit operations. */
+    tcg_target_available_regs[TCG_TYPE_I64] = BIT(TCG_TARGET_NB_REGS) - 1;
+    /*
+     * The TCI "registers" are in the local stack frame and
+     * cannot be clobbered by the called helper functions. Additionally, Wasm
+     * modules for a TB and QEMU itself (i.e. helpers) are separated so also
+     * those variables aren't clobbered by the called helper functions.
+     * However, the TB assumes a 128-bit return value and assigns to
+     * the return value registers.
+     */
+    tcg_target_call_clobber_regs =
+        MAKE_64BIT_MASK(TCG_REG_R0, 128 / TCG_TARGET_REG_BITS);
+
+    s->reserved_regs = 0;
+    tcg_regset_set_reg(s->reserved_regs, TCG_REG_TMP);
+    tcg_regset_set_reg(s->reserved_regs, TCG_REG_CALL_STACK);
+
+    /* The call arguments come first, followed by the temp storage. */
+    tcg_set_frame(s, TCG_REG_CALL_STACK, TCG_STATIC_CALL_ARGS_SIZE,
+                  TCG_STATIC_FRAME_SIZE);
+}